Field of the Invention
The present invention relates to a liquid ejection head that ejects liquid by using a piezoelectric transducer.
Description of the Related Art
Up to now, a liquid ejection recording apparatus configured to record an image on a recording medium by ejecting liquid has been proposed as a recording apparatus. A liquid ejection head that ejects liquid is mounted on the liquid ejection recording apparatus. As a liquid ejection mechanism of the liquid ejection head, a mechanism has been proposed in which a piezoelectric transducer represented by piezoelectric zirconate titanate (PZT) is provided in a pressure chamber, and introduction and ejection of the liquid are performed by changing an inner volume of the pressure chamber. The pressure chamber communicates with both a liquid supply path through which the liquid is supplied and an ejection port from which the liquid is ejected. At the time of shrinkage of the pressure chamber, the liquid in the pressure chamber is ejected from the ejection port as a droplet, and at the time of expansion of the pressure chamber, the liquid is supplied from the liquid supply path to the pressure chamber.
In recent years, there has been a demand for recording to be performed with high image quality at high speed. To realize such recording, a large number of ejection ports are to be arranged at a high density, and a large number of drive wirings for driving piezoelectric transducers corresponding to the respective ejection ports are to be led. For this reason, since the number of connection points with external wirings (for example, flexible printed circuits (FPC)) for connecting the drive wirings to a drive circuit of the piezoelectric transducers is increased, the space between the wirings is reduced, and there is a concern that arranging the wirings becomes difficult. In view of the above, PCT Japanese Translation Patent Publication No. 2012-532772 proposes a technology for addressing the above-described problem. PCT Japanese Translation Patent Publication No. 2012-532772 discloses the technology with which the drive wirings of the piezoelectric transducers, the drive circuit of the piezoelectric transducers, and the paths for supplying ink to the pressure chambers are integrally formed on a wiring substrate, which is bonded to a liquid ejection substrate provided with the pressure chambers and the ejection ports. Accordingly technology, provision of external wirings is avoided.
According to the technology disclosed in PCT Japanese Translation Patent Publication No. 2012-532772, after the drive circuit of the piezoelectric transducers and flow paths of through holes are formed on a wiring substrate constituted by a silicon substrate, the wiring substrate is bonded to the liquid ejection substrate. However, carrying out a process of forming the through holes and the like on the single silicon substrate and a process of forming semiconductor elements constituting the drive circuit involves technical difficulty. In addition, a wiring substrate on which a dedicated-use drive circuit is formed in accordance with a configuration and a shape of the liquid ejection head is to be designed and manufactured.
In view of the above, a mode is conceivable in which the drive wirings of the piezoelectric transducers and the drive circuit of the piezoelectric transducers are formed on separate members, and the drive wirings and the drive circuit are connected to each other by external wirings. In the liquid ejection head in which a large number of piezoelectric transducers are used, in general, the respective piezoelectric transducers are sandwiched between individual electrodes and a common electrode. The individual electrodes are individually connected to the respective piezoelectric transducers. The common electrode is commonly connected to all the piezoelectric transducers. The individual electrodes and the common electrode are connected to the external wirings via the drive wirings.
As described above, in a case where the common electrode is set to be common to all the piezoelectric transducers, variations of distances from the common electrode to the respective piezoelectric transducers become large, and differences in voltage drops in accordance with the distances also become large. Thus, variations of drive signals applied to the respective piezoelectric transducers also become large. As a result, the magnitude of ejection energy generated by the respective piezoelectric transducers to cause the liquid to be ejected from the ejection ports fluctuates, and ejection performance, such as ejection speed or ejection amount, may fluctuate in some cases.